Method for processing exceptional case of establishing default bearer in mobile communication system and device therefor

ABSTRACT

There are provided a method for processing an exceptional case of establishing a default bearer and a device therefor in order to solve a problem in that a user equipment cannot actually receive an IP service by accessing a packet network while failing in establishing the default bearer in a mobile communication system. A method for processing an exceptional case of establishing a default bearer in a mobility management entity includes: receiving a network attachment request from a user equipment; transmitting a network attachment acceptance including an activation request of the default bearer to the user equipment in response to the network attachment request; and cancelling a network attachment procedure when a completion response to the activation request of the default bearer is not received from the user equipment within a predetermined time.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 371, of PCTInternational Application No. PCT/KR2009/004471, filed Aug. 11, 2009,which claimed priority to Korean Application No. 10-2008-0078446, filedAug. 11, 2008 and Korean Application No. 10-2009-0068532, filed Jul. 27,2009 in the Korean Patent Office, the disclosures of which are herebyincorporated by reference.

TECHNICAL FIELD

An exemplary embodiment of the present invention relates to a method forprocessing an exceptional case of establishing a default bearer and adevice therefor.

BACKGROUND ART

An advanced third generation mobile communication system has introduceda concept of a default bearer in order to rapidly control various packetservices and facilitate management of a service quality. Upper layerservice context information for the default bearer is generated when auser equipment is firstly registered in a packet network and is alwayspresent in a terminal and a network regardless of signaling connectionbetween the user equipment and the packet network when the userequipment is registered in the packet network.

A resource is allocated to the default bearer while the signalingconnection between the user equipment and the packet network isestablished. When the signaling connection is cancelled, thecorresponding resource is also cancelled. Since an Internet protocol(IP) signaling packet (i.e., ICMP), an IP application signaling packet(i.e., SIP), or an IP packet (i.e., E-mail) having a service quality ofa ‘best-effort’ type are transmitted through the default bearer, thedefault bearer is the basis of the advanced third generation mobilecommunication system.

A procedure of establishing the default bearer is performed by beingincluded in an attachment procedure to be executed for the userequipment to firstly access the packet network. An exceptional case mayoccur in which only the attachment procedure is completed while thedefault bearer may not normally established due to various reasons.

At this time, even if the user equipment accesses the packet network,the user equipment cannot receive an IP service, a procedure forprocessing the exceptional case is required.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

DISCLOSURE OF INVENTION Technical Problem

The present invention has been made in an effort to provide a method forprocessing an exceptional case of establishing a default bearer infailing in establishing the default bearer and a device therefor.

Solution to Problem

An exemplary embodiment of the present invention provides a method forprocessing an exceptional case of establishing a default bearer in amobility management entity of a mobile communication system includes:receiving a network attachment request from a user equipment;transmitting a network attachment acceptance including an activationrequest of the default bearer to the user equipment in response to thenetwork attachment request; and cancelling a network attachmentprocedure when a completion response to the activation request of thedefault bearer is not received from the user equipment within apredetermined time.

Herein, cancelling the network attachment procedure includes determiningwhether or not the predetermined time elapses by using a timer andfurther includes retransmitting the network attachment acceptance to theuser equipment when the timer is expired while the completion responseto the activation request of the default bearer is not received.

Another embodiment of the present invention provides a device forprocessing an exceptional case of establishing a default bearer in amobile communication system includes: a communication unit that supportsa communication protocol for transmitting and receiving a request and aresponse depending on a network attachment procedure to and from a userequipment; and a control unit that transmits a network attachmentacceptance including an activation request of the default bearer inresponse to the network attachment request of the user equipment to theuser equipment and cancels the network attachment procedure when acomplete response to the activation request of the default bearer is notreceived from the user equipment within a predetermined time and furtherincludes a timer for determining whether or not the predetermined timeelapses.

Herein, the control unit retransmits a message of the network attachmentacceptance to the user equipment when the timer is expired while thecomplete response to the activation request of the default bearer is notreceived within the predetermined time.

Yet another embodiment of the present invention provides a method forprocessing an exceptional case of establishing a default bearer in amobility management entity of a mobile communication system includes:receiving a network attachment request from a user equipment;transmitting a network attachment acceptance including an activationrequest of the default bearer to the user equipment in response to thenetwork attachment request; and cancelling a network attachmentprocedure when a complete response to the activation request of thedefault bearer is not received from the user equipment until a timer isexpired at the predetermined times.

Herein, cancelling the network attachment procedure includes:retransmitting the network attachment acceptance to the user equipmentwhenever the timer is expired; and reactuating the timer afterretransmitting the network attachment acceptance.

There is provided a reliable IP service by providing an operationalprocedure for an exceptional case in which only an attachment procedureis completed while a default bearer is not normally established.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram illustrating a configuration of anadvanced third generation mobile communication system.

FIG. 2 illustrates a protocol stack of a control plane of an advancedthird generation mobile communication system according to an exemplaryembodiment of the present invention.

FIGS. 3 and 4 are flowcharts illustrating a method of establishing adefault bearer for each step according to an exemplary embodiment of thepresent invention.

FIG. 5 is a block diagram illustrating a configuration of a mobilitymanagement entity that processes an exceptional case of establishing adefault bearer according to an exemplary embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following detailed description, only certain exemplaryembodiments of the present invention have been shown and described,simply by way of illustration. Accordingly, the drawings and descriptionare to be regarded as illustrative in nature and not restrictive. Likereference numerals designate like elements throughout the specification.In the specification, unless explicitly described to the contrary, theword “comprise” and variations such as “comprises” or “comprising”, willbe understood to imply the inclusion of stated elements but not theexclusion of any other elements.

In the specification, a user equipment (UE) may designate a mobileterminal (MT), a mobile station (MS), a terminal, a subscriber station(SS), a portable subscriber station (PSS), an access terminal (AT), etc.or and may include the entire or partial functions of the mobileterminal, the terminal, the mobile station, the subscriber station, theportable subscriber station, the access terminal, etc.

In the specification, an evolved Node-B may designate a base station(BS), an access point (AP), a radio access station (RAS), a node-B, abase transceiver station (BTS), a mobile multihop relay (MMR)-BS, etc.and may include the entire or partial functions of the BS, the AP, theRAS, the node-B, the BTS, the MMR-BS, etc.

FIG. 1 is a schematic block diagram illustrating a configuration of anadvanced third generation mobile communication system.

In the embodiment, the mobile communication system includes a userequipment (UE) 110, an evolved Node-B (eNB) 120, an access gateway (aGW)130, and a mobility management entity (MME) 140.

The user equipment 110 accesses the eNB 120 through a wireless interfaceand the eNB 120 accesses the access gateway 130 through a wiredinterface. Further, the access gateway 130 is connected to an externalpacket data network (PDN) 150 through an Internet protocol (IP)interface. The mobility management entity 140 supports a controlprotocol of the third generation mobile communication system, andcontrols a packet service and a bearer through a signaling procedurewith the user equipment 110.

The user equipment 110 performs IP-based packet transmission andreception with a server (not shown) located on the packet data network150 or a corresponding node (not shown). The bearer needs to beestablished among the user equipment 110, the eNB 120, and the accessgateway 130 in order to transmit and receive IP packets.

The user equipment 110 can establish one or more bearers for one packetdata network 150. The bearer includes a default bearer that is basicallyestablished with address allocation at the time of accessing each packetdata network and a dedicated bearer that is additionally established bya request of quality of service (QoS) at the time of performing aservice. The embodiment of the present invention relates to a processingprocedure when the default bearer of two bearers is not normallyestablished.

FIG. 2 illustrates a protocol stack of a control plane of an advancedthird generation mobile communication system according to an exemplaryembodiment of the present invention.

In FIG. 2, the protocol stack of the control plane for the userequipment includes an evolved session management (ESM) layer 201 thatmanages a session including the default bearer, an evolved mobilitymanagement (EMM) layer 202 that manages mobility, a radio resourcecontrol (RRC) layer that manages a radio resource, a radio link controllayer (RLC) layer that controls a radio link, a media access control(MAC) layer that controls access of media, and a physical (PHY) layerwhich is a physical layer.

Further, In FIG. 2, the protocol stack of the control plane for themobility management entity includes an evolved session management (ESM)layer 203 that manages a session including the default bearer and anevolved mobility management (EMM) layer 204 that manages mobility, andin addition, includes an SI application (S1AP) layer, a user datagramprotocol (UDP) layer, an Internet protocol (IP) layer, layer 2 (L2)layer, and a layer 1 (L1) layer.

Hereinafter, a method of establishing the default bearer according to anexemplary embodiment of the present invention will be described withreference to the protocol stack of the control plane of FIG. 2.

FIGS. 3 and 4 are flowcharts illustrating a method of establishing adefault bearer for each step according to an exemplary embodiment of thepresent invention.

Referring to FIG. 3, when the user equipment 110 firstly accesses thepacket data network 150, the ESM layer 201 of the user equipment 110requests the EMM layer 202 to perform an attachment procedure in thepacket data network (S301). The EMM layer 202 that receives theattachment request transmits an attachment request message (i.e.,ATTACH_REQUEST) to the mobility management entity 140 through the eNB120 (S302).

The mobility management entity 140 that receives the attachment requestmessage establishes an RRC connection to allocate the resource to theuser equipment 110 (S303) and performs an authentication procedure ofthe user equipment 110 (S304). When authentication is successivelyperformed, the EMM layer 204 of the mobility management entity 140transmits an attachment acceptance message (i.e., ATTACH_ACCEPT) to theuser equipment 110 (S305). The attachment acceptance message includes amessage (i.e., Active_Default_EPS_Bearer_Context_Request) of requestingthe user equipment 110 to activate the default bearer.

Thereafter, the ESM layer 203 of the mobility management entity 140drives a predetermined timer (i.e., T3485 timer or T3450 timer) forsupervising whether or not the default bearer is activated in the userequipment 110 (S306). If a response message (i.e.,Active_Default_EPS_Bearer_Context_Complete or ATTACH_COMPLETE) to theactivation request of the default bearer is not received from the userequipment 110 (S308) until the timer is expired (S307), the ESM layer203 cancels the resource allocated for establishing the default bearerat step S303 (S309) and notifies a failure in establishing the defaultbearer to the EMM layer 204 of the mobility management entity 140(S310).

The EMM layer 204 that receives the notification of the failure inestablishing the default bearer initializes all establishments for theuser equipment 110 and waits to receive the attachment acceptancemessage again (S311).

If the response message (i.e.,Active_Default_EPS_Bearer_Context_Complete or ATTACH_COMPLETE) to theactivation request of the default bearer from the user equipment 110before the timer is expired at step S307 (S308), attachment of the userequipment 110 to the network is normally completed. (S312).

A time taken to activate the default bearer may be longer than apredetermined time set in the timer. For this, the ESM layer 203 of themobility management entity 140 can determine the failure in establishingthe default bearer or not through an expiration frequency of the timer.FIG. 4 is a flowchart illustrating a processing procedure in this case.

In FIG. 4, steps S401 to S406 and steps S409 to S411 are the same assteps S301 to S306 and steps S309 to S311 of FIG. 3. Therefore, stepsS407 and S408 will be described herein.

That is, the ESM layer 203 of the mobility management entity 140reactuates the timer until the timer is expired at the n−1-th times (nis a natural number equal to or larger than 2), but if the responsemessage (i.e., Active_Default_EPS_Bearer_Context_Complete orATTACH_COMPLETE) to the activation request of the default bearer is notreceived from the user equipment 110 (S408) until the timer is expired(S407) at the n-th times, the ESM layer 203 cancels the resourceallocated for establishing the default bearer at step S403 (S409) andnotifies the failure in establishing the default bearer to the EMM layer204 of the mobility management entity 140 (S410).

For example, the ESM layer 203 reactuates the timer until the timer isexpired at the 4-th times, but if the response message to the activationrequest of the default bearer is not received from the user equipment110 until the timer is expired at the 5-th times, the ESM layer 203cancels the resource allocated for establishing the default bearer andnotifies the failure in establishing the default bearer to the EMM layer204.

The EMM layer 204 that receives the notification of the failure inestablishing the default bearer initializes all establishments for theuser equipment 110 and waits to receive the attachment acceptancemessage again (S310).

Even when the default bearer is not established, an access to thecorresponding packet data network is possible, but an actual IP serviceis impossible, such that an incomplete access is made. However, if thedefault bearer is not established up to a predetermined time or atemporary identifier is not reallocated, an operation of the EMM layeris initialized through the notification of the failure to disableaccessing the packet data network and allow the establishment procedureof the default bearer to be re-executed in the initialization state.

FIG. 5 is a block diagram illustrating a configuration of a mobilitymanagement entity 140 that processes an exceptional case of establishinga default bearer according to an exemplary embodiment of the presentinvention. The mobility management entity 140 of the embodiment includesa communication unit 141, an ESM control unit 142, an EMM control unit143, a timer 144, and a memory 145.

The communication unit 141 transmits and receives various message for anetwork connection and a mobility management to and from the userequipment 110 through the eNode-B 120 under the control of the EMMcontrol unit 143.

When the ESM control unit 142 receives the attachment request message ofthe user equipment 110 through the communication unit 141, the ESMcontrol unit 142 allocates the resource to the user equipment 110 byestablishing the RRC connection and performs an authentication procedureof the user equipment 110. The mobility management entity 140 includesthe memory 145 that stores user authentication information.

When the authentication is successively performed, the ESM control unit142 transmits to the EMM control unit 143 of the mobility managemententity 140 a request message (i.e.,Active_Default_EPS_Bearer_Context_Request) for activating the defaultbearer to the user equipment 110. The EMM control unit 143 transmits theattachment acceptance message (i.e., ATTACH_ACCEPT) including theactivation request of the default bearer to the user equipment 110.

The ESM control unit 142 actuates the timer 144 (i.e., T3485 timer orT3450 timer) just after the ESM control unit 142 transmits the requestmessage for activating the default bearer or just after the EMM controlunit 143 transmits the attachment acceptance message. In addition, whenthe default bearer is not activated with respect to the activationrequest of the default bearer until the timer 144 is expired, the ESMcontrol unit 142 cancels the resource allocated for establishing thedefault bearer and notifies the failure in establishing the defaultbearer to the EMM control unit 143. When the failure in establishing thedefault bearer is notified from the ESM control unit 142, the EMMcontrol unit 143 initializes all establishments for the user equipment110.

The ESM control unit 142 can determine the failure in establishing thedefault bearer or not in accordance with an expiration frequency of thetimer 144. In other words, the ESM control unit 142 reactuates the timeruntil the timer 144 is expired at the n−1-th times (n is a naturalnumber equal to or larger than 2), but when the default bearer is notactivated until the timer is expired at the n-th times, the ESM controlunit 142 cancels the resource allocated for establishing the defaultbearer and notifies the failure in establishing the default bearer tothe EMM control unit 143. As one example, the ESM control unit 142reactuates the timer until the timer 144 is expired at the 4-th times,but when default bearer is not activated until the timer is expired atthe 5-th times, the ESM control unit 142 cancels the resource allocatedfor establishing the default bearer and notifies the failure inestablishing the default bearer to the EMM control unit 143

The above-mentioned exemplary embodiments of the present invention arenot embodied only by a method and apparatus. Alternatively, theabove-mentioned exemplary embodiments may be embodied by a programperforming functions that correspond to the configuration of theexemplary embodiments of the present invention, or a recording medium onwhich the program is recorded. These embodiments can be easily devisedfrom the description of the above-mentioned exemplary embodiments bythose skilled in the art to which the present invention pertains.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

The invention claimed is:
 1. A method for processing an exceptional case of establishing a default bearer in a mobility management entity (MME) of a mobile communication system, comprising: receiving a network attachment request from a user equipment as part of a network attachment procedure; transmitting a network attachment acceptance with an activation request of the default bearer to the user equipment in response to the network attachment request; and cancelling, by the MME, the network attachment procedure when a completion response to the activation request of the default bearer is not received from the user equipment within a predetermined time.
 2. The method of claim 1, wherein cancelling the network attachment procedure includes determining whether or not the predetermined time elapses by using a timer.
 3. The method of claim 2, wherein cancelling the network attachment procedure further includes retransmitting the network attachment acceptance to the user equipment when the timer is expired while the completion response to the activation request of the default bearer is not received.
 4. The method of claim 3, wherein: the network attachment acceptance is retransmitted until the timer is expired at the n-1-th times (n is a natural number equal to or larger than 2), and cancelling the network attachment procedure includes cancelling the network attachment procedure when the complete response to the activation request of the default bearer is not received until the timer is expired at the n-th times.
 5. The method of claim 4, wherein the n is
 5. 6. The method of claim 1, wherein: the mobility management entity includes a session management layer and a mobility management layer, and wherein transmitting the network attachment acceptance includes, allowing the session management layer to transmit the activation request of the default bearer to the mobility management layer; and allowing the mobility management layer to transmit the network attachment acceptance with the default bearer activation request to the user equipment.
 7. The method of claim 1, wherein: the mobility management entity includes the session management layer and the mobility management layer, and, cancelling the network attachment procedure further includes, allowing the session management layer to notify a failure in establishing the default bearer to the mobility management layer.
 8. The method of claim 1, wherein cancelling the network attachment procedure includes releasing an allocated resource for establishing the default bearer.
 9. The method of claim 1, wherein when a time taken to activate the default bearer is longer than the predetermined time, the mobility management entity determines the failure in establishing the default bearer through an expiration frequency of a timer.
 10. The method of claim 1, wherein the cancelling comprises cancelling a resource allocated for establishing the default bearer when the completion response to the activation request of the default bearer is not received from the user equipment within the predetermined time.
 11. A device for processing an exceptional case of establishing a default bearer in a mobile communication system, comprising: a communication unit that communicates with a user equipment; and a control unit, including at least one processing device, that transmits a network attachment acceptance with an activation request of the default bearer in response to the network attachment request of the user equipment to the user equipment and cancels the network attachment procedure when a complete response to the activation request of the default bearer is not received from the user equipment within a predetermined time.
 12. The device of claim 11, further comprising a timer for determining whether or not the predetermined time elapses.
 13. The device of claim 12, wherein the control unit retransmits a message of the network attachment acceptance to the user equipment when the timer is expired while the complete response to the activation request of the default bearer is not received within the predetermined time.
 14. The device of claim 13, wherein: the control unit retransmits the network attachment acceptance until the timer is expired at the n-1-th (n is a natural number equal to or larger than 2) times, and cancels the network attachment procedure when the complete response to the activation request of the default bearer is not received until the timer is expired at the n-th times.
 15. The device of claim 14, wherein the n is
 5. 16. The device of claim 12, wherein: the control unit includes an evolved session management (ESM) control unit and an evolved mobility management (EMM) control unit, and wherein when the ESM control unit transmits the activation request of the default bearer to the EMM control unit, the EMM control unit the network attachment acceptance with the activation request of the default bearer to the user equipment.
 17. The device of claim 16, wherein when the complete response to the activation request of the default bearer is not received from the user equipment within a predetermined time, the ESM control unit notifies a failure in establishing the default bearer to the EMM control unit.
 18. The device of claim 11, wherein the control unit releases an allocated resource for establishing the default bearer and cancels the network attachment procedure when a complete response to the activation request of the default bearer is not received from the user equipment within a predetermined time.
 19. A method for processing an exceptional case of establishing a default bearer in a mobility management entity (MME) of a mobile communication system, comprising: receiving a network attachment request from a user equipment as part of a network attachment procedure; transmitting a network attachment acceptance with an activation request of the default bearer to the user equipment in response to the network attachment request; and cancelling, by the MME, the network attachment procedure when a complete response to the activation request of the default bearer is not received from the user equipment until a timer is expired at the predetermined times.
 20. The method of claim 19, wherein cancelling the network attachment procedure further includes retransmitting the network attachment acceptance to the user equipment whenever the timer is expired and restarting the timer. 